Radiofrequency amplifier



RADI 0 FREQUENCY AMPLIFIER Filed Sept. 8, 1924 Jar/72 2/1 62/20.

atented Nor. 3,ll@25. I

SAMUEL COHEN, OF BROOKLYN, NEW YORK, ASSIGNOR TO OSODAMJPA CORPORA'fION,

0F YORK, N. Y., A CQRPOBATION, OF NEW YORK.

RADIQFREQUENGY AMPLIFIER.

Application filed Septembert, 192% Serial No. 736,603.

To all whom it may concern:

Be it known that if, SAMUEL citizen of the United States, residing at Brooklyn, in the county of Kings and State of New York, have invented a certain new and useful improvement in a Radiofrequency Amplifier, of which the following is a specification. I

My invention relates broadly to the amplification of feeble currents by electron tube circuits and more particularly to a radio frequency amplification system of great sensitivity.

" One of the objects of my invention is to provide a radio frequency amplification system for the reception of high frequency signaling currents, wherein both straight amplification and regenerative amplification is secured without distortion of the received signals. I

Another object of my invention is to provide a combined direct amplifying electron tube system and a regenerative amplifying electron tube system associated with a detector circuit with means for controlling the regenerative amplification for preventing undesired reaction with other electron tube circuits in the system.

Still another object of the invention is to provide a construction of regenerativecom pensator for connection in the last stage of amplification in a radio frequency amplifier immediately preceding the detector circuit for securing a large amplitude of radio frequency energy which may be impressed upon the input circuit of the detector for operating a responsive device.

A further object of the invention is to provide -a construction of coupling system interposed between a radio frequency amplification system and a detector system for increasing the energy in the detector circuit by regenerative action with means for pre-. venting regenerative effects in the amplification stages preceding the coupling system and allowing regeneration below a point of oscillation in the coupling system for impressing the received signaling energy at large ampl tude upon the detector.

Other objects of my invention will be understood from the specification hereinafter following by reference'to the 300011 1 panying drawing showing a diagrammatlc arrangement of my radio frequency amplification system.

COHEN, a

such a manner as to prevent distortion'in v l-leretofore in the art it has been proposed to regulate regeneration in a radio frequency amplifier by means of a. potentiometer shunted across the filament circuit of the amplifier with a connection to the grid electrodes of the several tubes of the system from a variable contact member upon the potentiometer,

"With the potentiometer method, regenera-. tion can be stopped when the grids ofthe amplifier tubes are maintained at'positive potential; lhis method of control is not an efficient one, since by causing the grids to be at a positive potential a large drain on the B battery is efi'ective. At the same time distortion of the signaling energy is" brought about and the amplification is considerably reduced. 'With the regenerator compensator method of my invention these disadvantages are overcome since the grid. electrodes are maintained at all times at a negative potential. The amount of'regen eration is controlled by, the amount of a counter E. introduped in the circuit, whose amplitude may beequal or greater than the regenerative E. M. 1F. ln all cases it can be made equal but opposite in-phase to the regenerative E. M. F

By the arrangement of the regenerative compensator the sensitivity of the system is greatly increased. The regenerative action of a tube is employed at such an adjustment that this regenerative action operates in the system. To do this, I prefer to make or allow :the amplifying tube next to the detector tube to operate in a state of regeneration. At the same'time I prbvide means for preventing regeneration by self excitation in the tube circuits immediately preceding the regenerative compensator. I employ a variable capacityof a special character which is connected .with an independent. winding forming part of the primary circuit of the inter-valve coupling transformer. By means of'the combination of this special capacity and inductance, I can control the amount of regeneration as desired. The grid electrode ofthe tube in the regenerator coupling circuit is maintained permanently at negative potential.

The regenerative compensator'consists of two parallel electrodes or plates .whose capacity is equal to approximately five times the grid-plate capacity. A movable mem her or electrode is placed within the center of the parallel plates, Which movable plate has an area slightly larger than the area of the parallel plates. lVhen the entire area of the movable plate is in the electrostatic field of the parallelplates the electrostatic capacity between the parallel plates is reduced to a minimum by virtue of the circuit arrangement. The regenerative action is obtained the stage of amplification immediately preceding the detector. The output circuit of this tube contains a 'pair of coils. forming the primary winding of the couapplied in connection with three stages of tuned radiofrequency amplification at a radio receiver although it will be'understood that more or less stages may be employed as desired. The antenna is represented by reference character 1 connected with ground system 2 with primary wind: ing 3 of the tuning transformer in circuit therewith. Secondary winding 5 is inductively related .to primary winding -3 and is tuned by variable condenser 6 to the frequency of the signals desired to be received. The first stage of radio frequency amplification includes electron tube 7 having filament electrode 8,-grid electrode 9, and.

plate electrode 10. The input circuit of the tube across grid electrode 9 and filament electrode 8 is connected with the tuned circuit 5- and 6. The output circuit of tube 7 includes primary winding 11 of the radio frequency coupling transformer 15 with one end of the winding 11 connected to a source of B battery potential represented at 1 1. The secondary winding 16 of coupling transformer 15 istuned by variable condenser 17 and connects to the input circuit of electron tube 18 forming the second stage of radio frequency amplification. The output circuit of tube 18 includes primary winding 19 of coupling transformer 20 and source of B battery potential 14;. The tubes 7 and 18 are connected in such manner that the tendency of the tubes to oscillate 'or regenerate is annulled. This is accomplished by employing the principle set forth in de tail in my copending application Serial No. 736,602, filed Sept. 8; 1924, wherein the resistancs and capacities R and C are electrically related to the inherent tube capacities for shifting the phase of interfering currents with respect to; the phase of the meoeea signaling currents. I therefore provide a radio frequency amplifier wherein a number of stages operate as straight amplifiers with:

outregeneration or oscillation. Tube 23; however, which immediately precedes the detector tube 33 is arranged for regenerative amplification, The input circuit of tube 23 is formed by secondary winding 21 of coupling transformer 20 tuned by variable condenser 22. Regeneration in the tube circuit 23 is controlled by means of the regenerator compensator 28-comprising parallel electrodes or plates 30 and 31 between which the movable member or electrode 29 is positioned .in such manner that the spacial relation with plate 31 or plate 30 may be regulated at will. A radio frequency coupling transformer 26 is connected in the .output circuit of tube 23. This coupling transformer includes a pair of primary windings 24 and 25 each having the same number of turns but wound in opposite directions. Each of the primary windings 24:

Referring more particularly to the re-' generator compensator 28, the primary winding 25 is connected with the movable plate or "electrode 29. The fixed plate 31 is connected with a point in the ouput circuit of. tube 23 at one end of the oppositely wound primary coil 24. The fixed plate or electrode 30 is connected indirectly with the opposite end of primary winding 21 through primary winding" 19 of coupling "transformer 20 in the output circuit of the precedingstage of radio frequency amplification formed in circuit with tube .18. The plate 29 has a larger area than plates30 and 31. The magnitude'of the counter E. M. F. introduced in the circuit is adjustable over a wide range by moving plate 29 either toward or away 'from the plates 30 and 31. The .regenerator compensator is so proportioned that the tube 23 will operate at maximum efficiency in condition of regenerative amplification forincreasing the amplitude of the received energy for detector tube 33.

VVhileI have, described my invention as applied to a three stageradio frequency amplifier it will be understood that the principle of my invention may be used With many arrangements of multistage amplifiers where a number of tubes areoperated with straightamplification while others of the tubes are operatedwith regenerative ampli- 1 ficationi The circuits formed by resistances and capacities R and C, prevent regeneration in tubes 7 and 18 while the regenerator compensator 28 permits regeneration under control of the operator in tube 23,, the circuits cooperating to maintain the entire system in stable condition/for the reception of signals without distortion. ll desire that it be understood that modifications of the circuit arrangements may be made and that I intend no limitations upon the-invention other than are imposedby the scope of the follows appended claims. 7

- at T claim and desire to secure by Letters Patent of the United ,States is as 1. A radio-frequency amplifier comprising in combination a plurality of electron tubes each having input and output circuits inter linked oneWith the other, a detector. con

nected with. the outputcircuit of oneofsaid tubes, means connected (between the in ut I and output circuits of said tubes immedia ely preceding the tube next adjacent said detector5for preventing regenerative amplifi cation and a three electrode condenser having two of its electrodes connected between the output circuit of said tube immediately precedin'gihe tube next adjacent said detector and the output circuit of said tube next adjacent said detector, and a connection between the third electrode of'said condenser and a separate winding magnetically coupled with the input circuit of said detector for. permitting regenerative amplification whereby receivedsignaling energy may be impressed at relatively large a'mplitude upon ,sa-id detector. o

v 2. A radio frequency amplifier including a detector, comprisin in combination a plurality "of electron tu es each having input I and outputcircuits interlinkedjone with the other, a coupling transformer 'interlinking the output circuit of one of said tubes with said detectbr,.saidtransformer having a pair ofgprimaiy windings, one of said wmdmgs being wound in a direction opposite to the electrostatic coupling between one of said windings and the output circuit ofa preoed- -ing one of said tubes and meanselectrodirection of the othervof said windings,an

statically coupling the other of said pri mary vwindings'with said afore mentioned electrostatic coupling.

3. A radio frequency amplifier including a detector, comprisin in combination a lurality of electron tu es each havlng input and output circuits interlinked one with the A other, means for coupling one ofsaid tubes with said detector comprising a pair of w introduced in said tube circuit by said oppositely wound primary coils whereby to re x I late the amount of regenerative amplificaton produced by said tube. v c 4. A radio frequency amplifier including a vdetector, comprising. a plurality of electron tubes each having'input and output circuits connected one with the other, 'means connected with a number of said tubes for prethe output circuit of another of said tubes venting'regenerative action, means coupling 7 with said detector, said means comprising a pair of oppositely wound primary coils coupled with a secondary coil, a pair of condenser plates, "a, connection between one of said plates and-one of said primary coils,

a connection between the other of said con 85. cuit of a preceding-gone of said tubes and denser plates and a point in the output cir-.

an intermediate condenser plate positioned:

between said pair of condenser plates and connected with one terminalof said ot e1" primary coil whereby regenerative amplifica= tion is secured in said last mentioned tube.

5. A radio frequency amplifier including .a detector comprising a plurality of electron tubes each having input and output circuits I connected one with the other, means con nected with a number ofs'aidtubes for. pre-' venting regenerative. action, means" cou-' p ling. the output circuiteof a'nbther f said tubes with said detector, said means comprising a pair of oppositely wound primary coils coupled with aseconda ycoil, a pair. of condenser plates, a connection between I one of said plates an'done ofsaidpri'mary coils, a connection between theother of'said condenser plates and a point in the output circuit jof-a preceding one of said tubes, a'

"separate condenser plate connected with the than said aforementioned condenser plates positioned intermediate said condenser. plates other of said-primary coilsgreater in size and adapted to be moved toward or away.

i from either of said aforementioned cons denser plates for controlling regenerative amplification in said last nentloned tube.

'. SAMUEL coHENn- 

